Reductive C−C Coupling from α,β‐Unsaturated Nitriles by Intercepting Keteniminates

We present an atom‐economic strategy to catalytically generate and intercept nitrile anion equivalents using hydrogen transfer catalysis. Addition of α,β‐unsaturated nitriles to a pincer‐based Ru−H complex affords structurally characterized κ‐N‐coordinated keteniminates by selective 1,4‐hydride transfer. When generated in situ under catalytic hydrogenation conditions, electrophilic addition to the keteniminate was achieved using anhydrides to provide α‐cyanoacetates in high yields. This work represents a new application of hydrogen transfer catalysis using α,β‐unsaturated nitriles for reductive C−C coupling reactions.Eine atomökonomische Strategie zur katalytischen Erzeugung und Verwendung von Nitrilanion‐Äquivalenten basiert auf Wasserstofftransferkatalyse. Die Addition von α,β‐ungesättigten Nitrilen an einen Ru‐H‐Pinzettenkomplex generiert durch selektiven 1,4‐Hydridtransfer Keteniminate, die in einer hydrierenden Acylierung eingesetzt wurden.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149558/1/ange201904530_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149558/2/ange201904530-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149558/3/ange201904530.pd

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Stereoretentive Deuteration of α‑Chiral Amines with D₂O

We present the direct and stereoretentive deuteration of primary amines using Ru-bMepi (bMepi = 1,3-(6′-methyl-2′-pyridyl­imino)­isoindolate) complexes and D₂O. High deuterium incorporation occurs at the α-carbon (70–99%). For α-chiral amines, complete retention of stereochemistry is achieved when using an electron-deficient Ru catalyst. The retention of enantiomeric purity is attributed to a high binding affinity of an imine intermediate with ruthenium, as well as to a fast H/D exchange relative to ligand dissociation

Role of Hemilabile Diamine Ligands in the Amine-Directed C–H Borylation of Arenes

A study of the role played by the bidentate ligand used in amine-directed C–H borylation is described. Both reaction conversion and selectivity were significantly impacted when steric congestion and electronic perturbations of the bidentate diamine ligand were made, but a more significant influence was imparted by reducing the bite angle of the ligand. <i>N</i>-Benzylaminopyridine was identified as a general ligand that improves both selectivity and yield for most problematic substrates previously reported with picolylamine as ligand

Intermediacy of Ni–Ni Species in sp² C–O Bond Cleavage of Aryl Esters: Relevance in Catalytic C–Si Bond Formation

Monodentate phosphine ligands are frequently employed in the Ni-catalyzed C–O functionalization of aryl esters. However, the extensive body of preparative work on such reactions contrasts with the lack of information concerning the structure and reactivity of the relevant nickel intermediates. In fact, experimental evidence for a seemingly trivial oxidative addition into the C–O bond of aryl esters with monodentate phosphines and low-valent nickel complexes still remains elusive. Herein, we report a combined experimental and theoretical study on the Ni(0)/PCy₃-catalyzed silylation of aryl pivalates with CuF₂/CsF additives that reveals the involvement of unorthodox dinickel oxidative addition complexes in C–O bond cleavage and their relevance in C–Si bond formation. We have obtained a mechanistic picture that clarifies the role of the additives and demonstrates that dinickel complexes act as reservoirs of the propagating monomeric nickel complexes by disproportionation. We believe this study will serve as a useful entry point to unravelling the mechanistic underpinnings of other related Ni-catalyzed C–O functionalization reactions employing monodentate phosphines

Intermediacy of Ni–Ni Species in sp² C–O Bond Cleavage of Aryl Esters: Relevance in Catalytic C–Si Bond Formation

Monodentate phosphine ligands are frequently employed in the Ni-catalyzed C–O functionalization of aryl esters. However, the extensive body of preparative work on such reactions contrasts with the lack of information concerning the structure and reactivity of the relevant nickel intermediates. In fact, experimental evidence for a seemingly trivial oxidative addition into the C–O bond of aryl esters with monodentate phosphines and low-valent nickel complexes still remains elusive. Herein, we report a combined experimental and theoretical study on the Ni(0)/PCy₃-catalyzed silylation of aryl pivalates with CuF₂/CsF additives that reveals the involvement of unorthodox dinickel oxidative addition complexes in C–O bond cleavage and their relevance in C–Si bond formation. We have obtained a mechanistic picture that clarifies the role of the additives and demonstrates that dinickel complexes act as reservoirs of the propagating monomeric nickel complexes by disproportionation. We believe this study will serve as a useful entry point to unravelling the mechanistic underpinnings of other related Ni-catalyzed C–O functionalization reactions employing monodentate phosphines

Intermediacy of Ni–Ni Species in sp² C–O Bond Cleavage of Aryl Esters: Relevance in Catalytic C–Si Bond Formation

Monodentate phosphine ligands are frequently employed in the Ni-catalyzed C–O functionalization of aryl esters. However, the extensive body of preparative work on such reactions contrasts with the lack of information concerning the structure and reactivity of the relevant nickel intermediates. In fact, experimental evidence for a seemingly trivial oxidative addition into the C–O bond of aryl esters with monodentate phosphines and low-valent nickel complexes still remains elusive. Herein, we report a combined experimental and theoretical study on the Ni(0)/PCy₃-catalyzed silylation of aryl pivalates with CuF₂/CsF additives that reveals the involvement of unorthodox dinickel oxidative addition complexes in C–O bond cleavage and their relevance in C–Si bond formation. We have obtained a mechanistic picture that clarifies the role of the additives and demonstrates that dinickel complexes act as reservoirs of the propagating monomeric nickel complexes by disproportionation. We believe this study will serve as a useful entry point to unravelling the mechanistic underpinnings of other related Ni-catalyzed C–O functionalization reactions employing monodentate phosphines

Intermediacy of Ni–Ni Species in sp² C–O Bond Cleavage of Aryl Esters: Relevance in Catalytic C–Si Bond Formation

Monodentate phosphine ligands are frequently employed in the Ni-catalyzed C–O functionalization of aryl esters. However, the extensive body of preparative work on such reactions contrasts with the lack of information concerning the structure and reactivity of the relevant nickel intermediates. In fact, experimental evidence for a seemingly trivial oxidative addition into the C–O bond of aryl esters with monodentate phosphines and low-valent nickel complexes still remains elusive. Herein, we report a combined experimental and theoretical study on the Ni(0)/PCy₃-catalyzed silylation of aryl pivalates with CuF₂/CsF additives that reveals the involvement of unorthodox dinickel oxidative addition complexes in C–O bond cleavage and their relevance in C–Si bond formation. We have obtained a mechanistic picture that clarifies the role of the additives and demonstrates that dinickel complexes act as reservoirs of the propagating monomeric nickel complexes by disproportionation. We believe this study will serve as a useful entry point to unravelling the mechanistic underpinnings of other related Ni-catalyzed C–O functionalization reactions employing monodentate phosphines

Iridium-Catalyzed, Substrate-Directed C–H Borylation Reactions of Benzylic Amines

The iridium-catalyzed arene C–H borylation reaction of benzylic amines has been developed, which inverts the typical steric-controlled product distribution to provide <i>ortho</i>-substituted boronate esters. Picolylamine was found to be an ideal ligand to replace 4,4′-di-<i>tert</i>-butylbipyridine to induce the directing effect. Preliminary experiments are consistent with a mechanism involving dissociation of one amine of the hemilabile diamine ligand